Encrypted 1-bit audio distribution system

ABSTRACT

An innovative system for transmitting encrypted 1-bit audio over an Ethernet network comprises using an omni-directional micro-electrical-mechanical system acoustic sensor element to provide an analog input signal to a sigma-delta modulator that then creates a pulse density modulated 1-bit data stream, at an audio oversampling rate, to a first input of a first exclusive-or (XOR) logic gate. The second input of the XOR logic gate is simultaneously presented with a first pseudo-random 1-bit data stream, at the same audio oversampling rate, thereby resulting in an encrypted pulse density modulated (PDM) 1-bit data stream at the output of the XOR logic gate. The encrypted PDM 1-bit data stream is clocked into a first-in first-out (FIFO) memory at the audio oversampling rate and is clocked out of the first FIFO memory as Ethernet PDM frame data packages at a predetermined Ethernet PHY transfer rate.

PRIORITY INFORMATION

The present application claims priority under 35 U.S.C. § 120 to U.S.Non-Provisional patent application Ser. No. 16/846,169, filed on Apr.10, 2020, the entire contents of which are expressly incorporated hereinby reference.

BACKGROUND OF THE INVENTION Technical Field

The embodiments described herein relate generally to audio datatransmission in teleconferencing settings, and more specifically tosystems, methods, and modes for securely distributing, with minimallatency, one or more 1-bit encrypted digital audio signals over anetwork using Internet protocol (IP).

Background Art

As those of skill in the art can appreciate, there are at least two mainmethods for encoding analog audio into digital data for storage andtransmission: pulse density modulation (PDM), and pulse code modulated(PCM). The latter, PCM, has been widely employed in such technologies asthe music industry, and especially for use with compact disks (CDs).Typically, such audio data is encoded using sixteen bits of resolutionat a sampling rate of either 44.1 kilohertz (kHz) or 48 kHz. Such highlevels of resolution are important in applications such as music storageand playing as many people have come to expect and appreciatehigh-fidelity audio systems.

In recent years, there has been increased interest in, and productsoffered for teleconferencing. That is, many new teleconference systemsare currently being offered that provide either or both audio and videointerfaces, with the audio-video (AV) data transmissions occurring overthe Internet in many cases, although in some settings, enterpriseentities may decide to use local networks (LANs) alone, ostensibly tocontrol security.

At the device level, a typical microphone such as one used on a personalcomputer or cell phone will use a combination of PDM and PCMtechnologies. PDM, as those of skill in the art can appreciate, uses asingle bit (technically a single stream of bits) to represent a sampledanalog audio input signal and PCM uses a stream of data words, each ofwhich represents the instantaneous amplitude of the sampled analog audioinput signal. Despite the inherent limitations of a one-bitrepresentation, it is possible to achieve extremely high audioperformance by sampling this audio at a very high rate, such as, forexample, a 2.82 Megahertz (Mhz) rate, which is a 64× oversampling of thetypical CD audio sampling rate of 44.1 kHz. These prior art microphonesconvert audio that is detected at an acoustic sensor element in ananalog-to-digital converter (ADC) that internally includes both asigma-delta (Σ-Δ) modulator and a filter decimator/lowpass filter tosequentially covert the analog audio first to PDM format and thendirectly to PCM format. It is known that a PCM format signal consumessubstantially less digital bandwidth than an equivalent PDM formatsignal.

FIG. 1 depicts method 200 for transmitting and receiving pulse codemodulated audio data using an Internet protocol, wherein the methodcomprises, among other steps, accepting an analog audio input at amicrophone, such as a micro-electro-mechanical system (MEMS) acousticsensor element (step 202), transferring the audio data over a digitalnetwork (step 210), and sending a corresponding analog output to aloudspeaker (step 220).

Referring now to FIG. 2 and continuing to refer to FIG. 1 , an IP PCMaudio transmitter 1 is based on a MEMS acoustic sensor element 11, that,for example, can be fabricated from a silicon wafer in the same mannerthat integrated circuits (IC) are manufactured. The MEMS acoustic sensorelement 11 functions as an acoustic transducer that converts soundpressure waves into an analog input signal 33 that is accepted (step202) by a Σ-Δ modulator 12 that converts (step 204) the analog inputsignal 33 into a PDM 1-bit data stream 32 having an update rate that isdetermined by a first audio oversampling clock 41 having a frequencythat is an integer multiple of the desired audio sampling rate. Forexample, given a desired audio sampling rate of 48 kHz and a sixty-fourtimes (64×) oversampling rate (OSR), the first audio oversampling clock41 would have an operational frequency of 3.072 MHz. Those skilled inthe art will recognize that a second order sigma-delta modulatoroperating at a 3.072 MHZ oversampling rate will provide acceptableCD-quality audio equivalent to, or better than, a 16-bit resolutiondigital signal that is updated at an audio sampling rate of 48 kHz.

The PDM 1-bit data stream 32 is decimated (step 206) into a 16-bit PCMN-bit digital data stream 31, by decimator filter 13, at an audiosampling rate that is determined by an audio sampling rate clock 42typically having a frequency of either 48 kHz or 44.1 kHz, as describedabove. The 16-bit PCM N-bit digital data stream 31 is packaged (step208) into Ethernet PCM frame data 34 by loading a first-in first-out(FIFO) memory 14 at the audio sampling rate, for example 48 kHz, andunloading the FIFO memory 14 at an Ethernet physical layer (PHY)transfer rate that is determined by an Ethernet PHY transfer rate clock43, typically having a frequency of 25 MHz. Those skilled in the art canappreciate that additional overhead data, such as a frame checksum, willbe required and that such data is typically computed by a processor andmemory 10 that is connected to the FIFO memory 14.

The Ethernet PCM frame data 34 is transmitted (step 210) from firstEthernet interface 16 as an Ethernet PCM transmission 35, containing onechannel of PCM, onto a network, such as a 100BaseT Ethernet LAN at arate of 100 million bits per second (Mbps), although those skilled inthe art will recognize that forty-eight thousand samples at sixteen bitsper sample will only account for 768 thousand bits per second or lessthan one percent (1%) of the available bandwidth.

Refer now to FIG. 3 , which shows prior art IP PCN audio receiver 2, andcontinue to refer to FIG. 1 . The Ethernet transmission containing onechannel of PCM data is received (step 210) at second Ethernet interface26, which then transfers the data contained within the transmission, inthe form of Ethernet PCM frame data 34, to FIFO memory 24. The EthernetPCM frame data 34 is reconstructed (step 212) into the 16-bit PCM N-bitdigital data stream 31 by loading a FIFO memory 24 at an Ethernet PHYtransfer rate that is determined by an Ethernet PHY transfer rate clock44, for example having a frequency of 25 MHz, and unloading the FIFOmemory 24 at an audio sampling rate that is determined by an audiosampling rate clock 45, for example having a frequency of 48 kHz. The16-bit PCM N-bit digital data stream 31 is converted (step 218) into ananalog output 36 by digital-to-analog converter (DAC) 27 and finally theanalog output 36 is sent (step 220) to loudspeaker 21. Those skilled inthe art can appreciate that additional overhead data, such as a framechecksum, will be required and that such data is typically computed by aprocessor and memory 20 that is connected to the FIFO memory 24.

Pulse Density Modulation

PDM, as those of skill in the art can appreciate, uses a single bit(technically a single stream of bits) to represent the analog audiosignal wherein the number of bits within a specific time period (bitdensity) is directly correlated with the amplitude of the audio signal.PDM can be a cost-effective way of conveying audio digitally. PDMrequires less wiring since it can be transmitted over a signal a pair oflines—one for a clock, and the second for the data. PDM operates atrelatively high clock frequencies, such as 64× the desired audiosampling rate, known as OSR. These high clock frequencies are beneficialbecause there is immunity from interfering signals in the audiofrequency band and despite the inherent limitations of a one-bitrepresentation of an audio signal, it is possible to achieve extremelyhigh audio performance with careful design.

Pulse Code Modulation

PCM is a well-known way of representing a varying analog signal as asequence, or stream, of N-bit data words, where N represents a power of2 and a higher value for N corresponds to a higher signal resolution.For example, a 3-bit PCM signal can represent eight discrete values. Inaddition, it is also known by those of skill in the art that such PCMformatted digital signals are produced by ADC operating at a fixed audiosampling rate.

The PCM output digital word can range from a few bits to many bits. Forexample, there exist ADCs with outputs ranging from 6-12 bits; thehigher number of bits the greater the resolution and the lessquantization error there is. However, as the number of bits in the ADCincreases so does the complexity of the circuitry needed to convert ananalog input signal into an “N” bit word. In addition, as the samplingfrequency increases so does the complexity of the ADC circuit design, ashigher frequency signals require different integrated circuitmanufacturing technologies and layout techniques for the IC and circuitboard the ADC will be used in. Thus, there are at least two bottlenecksto high speed high precision ADCs: high clocking frequencies, andgreater resolution.

PCM encoded audio has the advantage of being easy to manipulate usingdigital signal processing operations such as filtering operations. Suchfiltering operations use discrete Fourier Transforms (DFTs) to convertan audio signal from a time domain sampling representation to frequencydomain information. Other common audio processing functions such asmixing, equalization, and echo cancellation are also more readilyexecutable using PCM encoded audio than for example PDM encoded audio.

Long Felt Need

For existing network audio distribution as described above, audio istypically sampled in PDM format by a MEMS acoustic sensor element, butimmediately converted to PCM format at the IP PCM audio transmitter 1and transmitted in PCM format over a network to PCM audio receiver 2.This has the disadvantage of introducing a sampling latency because ofthe PDM to PCM conversion and data bus frame scheduling. Even morelatency would occur if it is required for the PCM formatted audio datato be encrypted and subsequently decrypted for network securitypurposes.

Since it is known that audio latency is undesirable for multi-microphonesystems, such as conference rooms, there is a long felt need to providesystems, methods, and modes for securely distributing, with minimallatency, digital audio signals over a network using IP. In addition,there has developed a recent awareness that most digital signals shouldbe encrypted due to security and privacy concerns. The inventiondescribed below fulfills this long felt need by encrypting one or more1-bit PDM formatted audio streams using a very low latency exclusive-or(XOR) logic gate encoding method which advantageously can also reducePDM-PCM conversion latency to a single audio sampling frame.

SUMMARY OF THE INVENTION

It is an object of the embodiments to substantially solve at least theproblems and/or disadvantages discussed above, and to provide at leastone or more of the advantages described below.

It is therefore a general aspect of the embodiments to provide systems,methods, and modes for securely distributing, with minimal latency, oneor more 1-bit encrypted digital audio signals over a network using IPthat will obviate or minimize problems of the type previously described.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

Further features and advantages of the aspects of the embodiments, aswell as the structure and operation of the various embodiments, aredescribed in detail below with reference to the accompanying drawings.It is noted that the aspects of the embodiments are not limited to thespecific embodiments described herein. Such embodiments are presentedherein for illustrative purposes only. Additional embodiments will beapparent to persons skilled in the relevant art(s) based on theteachings contained herein.

Aspects of the embodiments seek to overcome or at least ameliorate oneor more of several problems, including but not limited to distributingdigitized audio in an encrypted manner with minimal latency over an LAN.

DISCLOSURE OF INVENTION

According to a first aspect of the embodiments, a method fortransmitting encrypted audio data over an Ethernet connection isprovided, the method comprising: (a) converting (step 304) an audioinput signal (33) into a pulse density modulated 1-bit data stream (32)at a first predetermined audio oversampling rate; (b) producing (step307) an encrypted pulse density modulated 1-bit data stream (73) byXORing the pulse density modulated 1-bit data stream with a firstpseudo-random 1-bit data stream (78); (c) packaging (step 309) theencrypted pulse density modulated 1-bit data stream into Ethernet pulsedensity modulated frame data (74) by loading a first FIFO memory (54) atthe first predetermined audio oversampling rate and unloading said firstFIFO memory at a first predetermined Ethernet PHY transfer rate; (d)transmitting and receiving (step 310) said Ethernet frame data from afirst Ethernet interface (16) to a second Ethernet Interface (26); (e)reconstructing (step 313) the encrypted pulse density modulated 1-bitdata stream from the Ethernet frame data by loading a second FIFO memory(64) at a second predetermined Ethernet PHY transfer rate and unloadingsaid second FIFO memory at a second predetermined audio oversamplingrate; (f) recovering (step 315) the pulse density modulated 1-bit datastream by XORing the encrypted pulse density modulated 1-bit data streamwith a second pseudo-random 1-bit data stream (79); (g) decimating (step317) the pulse density modulated 1-bit data stream into a pulse codedmodulated N-bit digital data stream (31) at a predetermined audiosampling rate; and (h) converting (step 318) the N-bit pulse codemodulated digital data stream into an analog output signal (36); wherein(i) said first and second pseudo-random 1-bit data streams compriseidentical bit sequences at a predetermined encoding rate; and (ii) thesteps of producing and reconstructing the encrypted pulse densitymodulated 1-bit data stream by XORing are performed at saidpredetermined encoding rate.

According to the first aspect of the embodiments, the N-bit pulse codemodulated digital data stream is a 16-bit pulse code modulated digitaldata stream.

According to the first aspect of the embodiments, the first and secondpredetermined audio oversampling rates are both a same integer multipleof the predetermined audio sampling rate.

According to the first aspect of the embodiments, the predeterminedencoding rate is an integer multiple of the predetermined audio samplingrate.

According to the first aspect of the embodiments, said predeterminedaudio sampling rate is an integer multiple of the predetermined encodingrate.

According to the first aspect of the embodiments, the method furthercomprises: (a) transmitting and receiving a unique seed value (70) fromthe first Ethernet interface to the second Ethernet Interface; (b)computing said first pseudo-random 1-bit data stream based on thisunique seed value; and (c) computing said second pseudo-random 1-bitdata stream based on this unique seed value.

According to a second aspect of the embodiments, an internet protocol(IP) pulse density modulation (PDM) audio transmitter apparatus adaptedto transmit an encrypted PDM 1-bit data stream over an Ethernet networkis provided, said apparatus comprising: (a) an acoustic sensor element(11); (b) a sigma-delta modulator (12) adapted to convert an analoginput signal (33) into a pulse density modulated 1-bit data stream (32)at a predetermined audio oversampling rate; (c) a processor and memory(50) adapted to compute and produce a first pseudo-random 1-bit datastream (78) at a predetermined encoding rate; (d) a first exclusive-or(XOR) logic gate (58) operatively connected to the pulse densitymodulated 1-bit data stream and the pseudo-random 1-bit data stream insuch a manner as to produce an encrypted pulse density modulated 1-bitdata stream (73) at the predetermined audio oversampling rate; (e) afirst FIFO memory (54) configured to load the encrypted pulse densitymodulated 1-bit data stream at said predetermined audio oversamplingrate and to unload Ethernet pulse density modulated frame data (74) at apredetermined Ethernet PHY transfer rate; and (f) an Ethernet interface(16) configured to accept the Ethernet frame data at the predeterminedEthernet PHY transfer rate and to transmit Ethernet data packets on anetwork.

According to the second aspect of the embodiments said acoustic sensorelement is a micro-electrical-mechanical system acoustic sensor element.

According to the second aspect of the embodiments, said predeterminedaudio oversampling rate is an integer multiple of the predeterminedencoding rate.

According to the second aspect of the embodiments, the processor andmemory are further adapted to: (a) compute a frame checksum (FCS; 712);(b) compute a payload preamble (806); and (c) load each of said Ethernetframe checksum and payload preamble into the FIFO memory.

According to the second aspect of the embodiments, the payload preambleincludes a time stamp.

According to the second aspect of the embodiments, the processor andmemory are further adapted to: (a) store a predetermined FCS delay gap(710); (b) store a predetermined interframe gap (714); (c) store apredetermined Ethernet frame prefix (802); (d) store a predeterminedIP/UDP prefix (804); and (e) load each of said FCS delay gap, interframegap, Ethernet frame prefix, and IP/UDP prefix into the FIFO memory.

According to a third aspect of the embodiments, an internet protocolspeaker apparatus (6) adapted to receive a 1-channel encrypted PDM 1-bitdata stream over an Ethernet network is provided, said apparatuscomprising: (a) a first Ethernet interface configured to receiveEthernet data packets on a network; (b) a second FIFO memory (64)configured to load the Ethernet data packets at a predetermined EthernetPHY transfer rate and to unload an encrypted pulse density modulated1-bit data stream (73) at a second predetermined audio oversamplingrate; (c) a processor and memory (60) adapted to compute and produce asecond pseudo-random 1-bit data stream (79) at a predetermined encodingrate; (d) a second XOR logic gate (68) operatively connected to theencrypted pulse density modulated 1-bit data stream and thepseudo-random 1-bit data stream in such a manner as to produce anunencrypted pulse density modulated 1-bit data stream (32) at saidpredetermined audio oversampling rate; (e) a decimator filter (13)adapted to convert the unencrypted pulse density modulated 1-bit datastream into a pulse code modulated N-bit digital data stream (31) at apredetermined audio sampling rate; (f) a digital to analog converter(27) adapted to convert the N-bit pulse code modulated digital datastream into an analog output signal (36) at said predetermined audiosampling rate; and (g) a loudspeaker (21) configured to receive theanalog output signal.

According to the third aspect of the embodiments, (a) the N-bit pulsecode modulated digital data stream is a 16-bit pulse code modulateddigital data stream.

According to the third aspect of the embodiments, (a) said predeterminedaudio oversampling rate is an integer multiple of the predeterminedencoding rate.

According to a fourth aspect of the embodiments, an internet protocol(IP) loudspeaker apparatus (9) adapted to receive a multi-channelencrypted PDM 1-bit data stream over an Ethernet network is provided,said apparatus comprising: (a) a second FIFO memory (64) configured toload Ethernet data packets at a predetermined Ethernet PHY transfer rateand to unload a plurality of encrypted pulse density modulated 1-bitdata streams (83A-83G) at a predetermined audio oversampling rate; (c) aprocessor and memory (90) adapted to compute and produce a plurality ofpseudo-random 1-bit data streams (89A-89G) at a predetermined encodingrate; (d) a plurality of XOR logic gates (98A-98G), each of said XORgates operatively connected to a corresponding one of said plurality ofencrypted pulse density modulated 1-bit data streams and a correspondingone of said plurality of pseudo-random 1-bit data streams in such amanner as to produce a corresponding plurality of unencrypted pulsedensity modulated 1-bit data streams (82A-82G) at said predeterminedaudio oversampling rate; (e) a plurality of decimator filters (93A-93G)adapted to convert each of said plurality of unencrypted pulse densitymodulated 1-bit data streams into a corresponding plurality of N-bitpulse code modulated digital data streams (81A-81G) at a predeterminedaudio sampling rate; (f) a digital audio mixer (99) configured to acceptthe plurality of N-bit pulse code modulated digital data streams and toproduce a combined pulse code modulated N-bit digital data stream (31)multi-channel output; (g) a digital to analog converter (27) adapted toconvert the combined PCM N-bit digital data stream into an analog outputsignal (37) at said predetermined audio sampling rate; and (h) aloudspeaker (21) configured to receive the analog output signal.

According to the fourth aspect of the embodiments, the combined PCMN-bit data stream is a PCM 16-bit digital data stream.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects and features of the embodiments will becomeapparent and more readily appreciated from the following description ofthe embodiments with reference to the following figures. Differentaspects of the embodiments are illustrated in reference figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered to be illustrative rather than limiting. Thecomponents in the drawings are not necessarily drawn to scale, emphasisinstead being placed upon clearly illustrating the principles of theaspects of the embodiments. In the drawings, like reference numeralsdesignate corresponding parts throughout the several views.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 illustrates a method, represented by sequential steps known inthe in the prior art, for accepting an analog audio input from anacoustic sensor element, digitizing this audio into 1-bit pulse densitymodulation (PDM) format, decimating this PDM formatted audio into PCMformat, and transmitting this PCM formatted audio via an Ethernetnetwork in a non-encrypted state, and finally using this audio to drivea loudspeaker.

FIG. 2 is a block diagram of a non-encrypted audio transmittingapparatus, such as would be known in the prior art, that converts aninput analog audio signal into a 1-bit PDM format having an OSR of 64×,where this signal is first decimated into a PCM format with 16-bitresolution and then transmitted via an Ethernet network.

FIG. 3 is a block diagram of a non-encrypted audio receiving apparatus,such as would be known in the prior art, that receives audio data via anEthernet network in a PCM format with 16-bit resolution and convertsthis data into an output analog audio signal which is used to drive aloudspeaker.

FIG. 4 illustrates an inventive method, whereby an input analog audiosignal is digitized into 1-bit PDM format, encoded by an XOR operationinto an encrypted 1-bit PDM data stream that is packaged and transmittedover a high speed Ethernet system by a first device, and then received,unencrypted, decimated into PCM format, and then converted into ananalog signal that is input to a loudspeaker according to certainillustrative embodiments of the present invention.

FIG. 5 is a block diagram of an encrypted 1-bit audio transmittingapparatus, according to an illustrative embodiment of the presentinvention.

FIG. 6 is a block diagram of an encrypted 1-bit audio receivingapparatus, suitable for receiving 1-channel PDM data, according to afirst illustrative embodiment of the present invention.

FIG. 7A illustrates a block diagram of a loading order of an Ethernetaudio data frame that is transmitted from the apparatus of FIG. 5 over anetwork and received by the apparatus of FIG. 6 according to aspects ofcertain embodiments of the present invention, and FIG. 7B illustrates ablock diagram of an unloading order of the Ethernet audio data framethat is transmitted from the apparatus of FIG. 5 over a network andreceived by the apparatus of FIG. 6 according to aspects of certainembodiments of the present invention.

FIG. 8 illustrates details of a transferal of data between a processorand memory and FIFO memory of the apparatus of FIG. 5 according toaspects of certain embodiments of the present invention.

FIG. 9 depicts an encrypted 1-bit audio distribution system including aplurality of inventive transmitting and receiving apparatuses connectedvia an Ethernet network using a router.

FIG. 10 is a block diagram of an encrypted 1-bit audio receivingapparatus, suitable for receiving multi-channel PDM data, according to asecond illustrative embodiment of the present invention.

LIST OF REFERENCE NUMBERS FOR THE MAJOR ELEMENTS IN THE DRAWING

The following is a list of the major elements in the drawings innumerical order.

-   1 IP PCM audio transmitter (prior art)-   2 IP PCM audio receiver (prior art)-   3 Ethernet router and processor-   5 IP PDM audio transmitter (per present invention)-   5A-5G Plurality of IP PDM audio transmitters (IP audio transmitter    5)-   6 IP PDM audio receiver (1-channel input)-   7 data (transferred between processor and memory 50 and first FIFO    memory 54)-   9 IP PDM audio receiver (multi-channel input)-   10 processor and memory (p/o IP PCM audio transmitter 1)-   11 MEMS acoustic sensor element (p/o of IP PCM audio transmitter 1)-   12 sigma-delta modulator (converts analog signal to PDM 1-bit data)-   13 decimator filter (converts PDM 1-bit data to PCM N-bit data)-   14 FIFO memory (packages PCM N-bit data into Ethernet packet)-   16 first Ethernet interface (transmitter)-   20 processor and memory (p/o IP PCM audio receiver 2)-   21 loudspeaker (p/o 1-channel IP PCM audio receiver 2)-   24 FIFO memory (unpackages Ethernet packet into PCM N-bit data)-   26 second Ethernet interface (receiver)-   27 digital to analog converter (converts PCM N-bit data into analog    signal)-   31 PCM N-bit digital data stream (representation of analog input    signal 33)-   32 PDM 1-bit data stream (representation of analog input signal 33)-   33 analog input signal (from acoustic sensor element 11)-   34 Ethernet PCM frame data (1-channel PCM data)-   Ethernet PCM transmission (1-channel PCM data)-   36 analog output signal (to loudspeaker 21)-   37 combined analog output signal (multi-channel output)-   41 first audio oversampling clock (frequency is integer multiple of    audio sampling rate clock 42)-   42 audio sampling rate clock-   43 Ethernet PHY transmit transfer rate clock-   44 Ethernet PHY receive transfer rate clock-   45 audio sampling rate clock-   46 second audio oversampling rate clock (same frequency as first    audio oversampling rate clock 41)-   50 processor and memory (p/o IP PDM audio transmitter 5)-   54 first FIFO memory (packages encrypted PDM 1-bit data stream 73    into Ethernet packet)-   58 first XOR logic gate (p/o IP PDM audio transmitter 5)-   60 processor and memory (p/o IP PDM audio receiver 6)-   64 second FIFO memory (unpackages 1-channel Ethernet packet into one    encrypted PDM 1-bit data stream 72)-   68 second XOR logic gate (p/o IP PDM audio receiver 6)-   70 unique seed value (used to create pseudo-random bitstream)-   73 encrypted PDM 1-bit data stream-   74 Ethernet PDM frame data (1-channel encrypted PDM data)-   75 Ethernet PDM transmission (1-channel encrypted PDM data)-   76 Combined Ethernet PDM transmission (multi-channel encrypted PDM    data)-   77 combined PCM N-bit data stream (combined multi-channel output    from digital audio mixer 99)-   78 first pseudo-random 1-bit data stream (from processor and memory    50)-   79 second pseudo-random 1-bit data stream (from processor and memory    60)-   81A-81G plurality of PCM N-bit data streams (from plurality of    decimator filters 93A-93G)-   82A-82G plurality of unencrypted PDM 1-bit data streams (from    plurality of XOR-   logic gates 98A-98G)-   83A-83G plurality of encrypted PDM 1-bit data streams (from FIFO    memory 94)-   89A-89G plurality of pseudo-random 1-bit data streams (from    processor and memory 90)-   90 processor and memory (p/o multi-channel IP PDM audio receiver 9)-   93A-93G plurality of decimator filters (p/o multi-channel IP PDM    audio receiver 9)-   94 FIFO memory (unpackages multi-channel Ethernet packet into a    plurality of unencrypted PDM 1-bit data streams 82A-82G)-   95A-95G plurality of pseudo random bit stream generators (p/o    processor and memory 90)-   98A-98G plurality of XOR logic gates (p/o multi-channel IP PDM audio    receiver 9)-   99 digital audio mixer (p/o multi-channel IP PDM audio receiver 9)-   100 networked digital audio distribution system-   200 Method for transmitting and receiving audio data encoded using    pulse code modulation using an Internet protocol-   202-220 Steps of Method 200-   300 Method for transmitting and receiving audio data encoded using    pulse density modulation using an Internet protocol-   302-320 Steps of Method 300-   551 checksum generator (p/o processor and memory 50)-   552 pseudo-random bit stream generator (p/o processor and memory 50)-   702 Ethernet frame prefix (frame N-1)-   704 IP/UDP prefix (frame N-1)-   706 payload preamble (frame N-1)-   709 encrypted PDM data payload (frame N-1)-   710 Frame Check Sum (FCS) delay gap (frame N-1)-   712 FCS checksum (frame N-1)-   714 interframe gap (frame N-1)

DETAILED DESCRIPTION OF THE INVENTION

The detailed description that follows is written from the point of viewof a control systems company, so it is to be understood that generallythe concepts discussed herein are applicable to various subsystems andnot limited to only a particular controlled device or class of devices,such as audio teleconferencing systems.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with an embodiment is included inat least one embodiment of the embodiments. Thus, the appearance of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout the specification is not necessarily referring to the sameembodiment. Further, the particular feature, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

The different aspects of the embodiments described herein pertain to thecontext of systems, methods, and modes for securely distributing, withminimal latency, one or more 1-bit encrypted digital audio signals overa network using Internet Protocols (IP), but is not limited thereto,except as may be set forth expressly in the appended claims.

The description below of the aspects of the embodiments, is bothnon-exclusive and non-limiting. The description below of the aspects ofthe embodiments is non-exclusive in that additional terms can or havebeen used, and it is non-limiting in that other meanings as defined inthe description below in view of the context of the aspects of theembodiments can be inferred therefrom. Thus, the following is meant as anon-limiting beginning guide to understanding the terms in view of theaspects of the embodiments

Refer now to FIGS. 4 and 5 . An Internet protocol (IP) PDM audiotransmitter 5 includes a MEMS acoustic sensor element 11. The MEMSacoustic sensor element 11 functions as an acoustic transducer thatconverts sound pressure waves into an analog input signal 33 that isaccepted (step 302) by Σ-Δ modulator 12 that converts (step 304) theanalog input signal 33 into PDM 1-bit data stream 32 having an updaterate that is determined by a first audio oversampling clock 41 which hasa frequency that is an integer multiple of the desired audio samplingrate. For example, given a desired audio sampling rate of 48 kHz and asixty-four times (64×) OSR, the first audio oversampling clock 41 wouldhave an operational frequency of 3.072 MHz. Those skilled in the artwill recognize that a second order sigma-delta modulator operating at a3.072 MHZ oversampling rate will provide acceptable CD-quality audioequivalent to, or better than, a 16-bit resolution digital signal thatis updated at an audio sampling rate of 48 kHz.

Next, an encrypted PDM 1-bit data stream 73 is produced (step 307) by anXOR logic gate operation, wherein the PDM 1-bit data stream 32 isapplied to a first input of first XOR logic gate 58, and a firstpseudo-random 1-bit data stream 78 is applied to a second input of firstXOR logic gate 58. The first pseudo-random 1-bit data stream 78 may becreated by processor and memory 50 based on a unique seed value 70 usingvarious algorithms that are known in the art.

The encrypted PDM 1-bit data stream 73 is packaged (step 309) intoEthernet PDM frame data 74, containing 1-channel encrypted PDM data(encrypted PDM 1-bit data stream 73), by loading a first FIFO memory 54at the first predetermined audio oversampling rate and unloading saidfirst FIFO memory 54 at a transfer rate that is determined by EthernetPHY transmit transfer rate clock 43.

The Ethernet PDM frame data 74 is transmitted (step 310) from a firstEthernet interface 16 as an Ethernet PDM transmission 75, containing1-channel encrypted PDM data, onto a network, such as a 100BaseTEthernet LAN at a rate of 100 Mbps.

Refer now to FIG. 6 and continue to refer to FIG. 4 . The Ethernet PDMtransmission 75, containing 1-channel encrypted PDM data is received(also step 310) at a second Ethernet Interface 26 which then transfersthe data contained within the transmission, in the form of Ethernet PDMframe data 74, to second FIFO memory 64.

The Ethernet PDM frame data 74 is reconstructed (step 313) into theencrypted PDM 1-bit data stream 73 by loading the second FIFO memory 64at a second predetermined Ethernet PHY transfer rate that is determinedby a second Ethernet PHY transfer rate clock 44, typically having afrequency of 25 MHz, and unloading said second FIFO memory 64 at asecond predetermined audio oversampling rate, determined by a secondaudio oversampling rate clock 46, which has a frequency matching that ofthe first audio oversampling rate clock 41, shown in FIG. 5 .

In method step 315, the PDM 1-bit data stream 32 is recovered by XORing,at second XOR logic gate 68, the encrypted PDM 1-bit data stream 73 witha second pseudo-random 1-bit data stream 79. A person skilled in the artcan appreciate that, when the first pseudo-random 1-bit data stream 78,shown in FIG. 5 , and the second pseudo-random 1-bit data stream 79contain an identical bit sequences, the XORing function of the secondXOR logic gate 68 will act to unencrypt data that has been encrypted dueto the XORing function of the first XOR logic gate 58, which is alsoshown in FIG. 5 . It is important to note that the steps of producing(step 307) and reconstructing (step 313) the encrypted pulse densitymodulated 1-bit data stream by XORing are performed at the samepredetermined encoding rate.

In method step 317, the PDM 1-bit data stream 32 is decimated into PCMN-bit digital data stream 31 at decimator filter 13 using apredetermined audio sampling rate that is determined by audio samplingrate clock 45.

In method step 318, PCM N-bit digital data stream 31 is converted intoan analog output signal 36 by DAC 27. Finally, the analog output signal36 is sent (step 320) to loudspeaker 21.

The encrypted PDM 1-bit data stream 73 is produced (step 307) by an XORlogic operation by combining the PDM 1-bit data stream 32 with firstpseudo-random 1-bit data stream 78. In recovering (step 315) the PDM1-bit data stream 32 is produced at the output of the second XOR logicgate 68 from the encrypted PDM 1-bit data stream 73 by using secondpseudo-random 1-bit data stream 79. According to aspects of theembodiments, the same pseudo random bit stream generation algorithm usedby processor and memory 50 is also used by processor and memory 60 togenerate identical bit streams from the same unique seed value 70.

In decimating (step 317) the pulse density modulated 1-bit data streamis decimated into a PCM N-bit digital data stream 31 by decimator filter13 at a predetermined audio sampling rate, using audio sampling rateclock 45, for example.

In converting (step 318) the N-bit pulse code modulated digital datastream is converted into an analog output signal 36 by DAC 27, whereinthe audio sampling rate is determined by an audio sampling rate clock 45typically having a frequency of either 48 kHz or 44.1 kHz, as describedabove.

Refer now to FIG. 7 and continue to refer to FIG. 5 . Ethernet PDMtransmission 75 comprises a series of Ethernet sub-frames, the sum ofwhich comprises Ethernet PDM frame data 75, where each Ethernetsub-frame is a data link layer protocol data unit that uses theunderlying Ethernet physical layer transport mechanisms. In other words,Ethernet PDM frame transmission 75 transports Ethernet sub-framesincluding data payloads and more specifically 1-channel encrypted PDMdata. That is, the Ethernet PDM transmission 75 is loaded in the ordershown in FIG. 7A and unloaded in the order shown in FIG. 7B. The loadingorder of FIG. 7A represents the order in which each Ethernet PDMtransmission is built at first FIFO memory 54, and the unloading orderrepresents the order in which the data within the Ethernet PDMtransmission 75 is unloaded.

In the loading order shown in FIG. 7A, the Ethernet frame comprisesEthernet frame prefix 702 that has a predetermined fixed value, InternetProtocol (IP)/User Defined Protocol (UDP) prefix 704 that also has apredetermined fixed value, payload preamble 706 that preferably includesa time stamp, encrypted PDM data payload 709 which corresponds toencrypted PDM 1-bit data stream 73, frame check sum (FCS) delay gap 710which comprises padding bits and allows for a time delay during which aframe check sequence (FCS)—checksum per Institute of Electrical andElectronics Engineers (IEEE) 802.3 is calculated, FCS checksum 712, andinterframe gap 714 that preferably includes a synchronization delay toensure that audio sampling rate is synchronized with Ethernet frametransmission rate. In a first embodiment of the present invention, 96000Ethernet frames per second (fps) are transmitted and each Ethernet frameincludes an encrypted PDM data payload 709 having 4 bytes (32 bits) ofdata. These 4 bytes of data represent one channel of audio, such as thatproduced by IP PDM audio transmitter 5.

It can be appreciated by those skilled in the art that up to eightchannels of audio data, consisting of 32 bytes (256 bits; i.e., eightchannels of Ethernet PDM frame data 74), can be contained in encryptedPDM data payload 709 within the overall timing constraint of 10.4 μsecthat is determined by maintaining an Ethernet frame rate of 96,000 fpsrate on a 100BaseT Ethernet network.

Attention is now directed to FIG. 7A, which shows an unloading ofEthernet PDM transmission 75. order As shown in FIG. 7A, the EthernetPDM transmission 75 is sequentially unloaded from first FIFO memory54—In order to minimize data latency, the encrypted PDM 1-bit datastream 73 is loaded over each entire Ethernet frame time period, forexample 10.4 μsec, but it is unloaded at just the end of that timeperiod so that the final bit of the 32 bits per Ethernet frame, of theencrypted PDM 1-bit data stream 73 is loaded into first FIFO Memory 54just before it is unloaded. In other words, the loading of the audiodata is spread out over the time period and unloading of the audio datais done in a burst.

Attention is now directed to FIG. 8 . Simultaneous with the loading of afirst portion of encrypted 1-bit data stream 73 for a current frame(Frame N), processor and memory 50 calculate the FCS Checksum 712 forthe proceeding frame (Frame N-1), using, for example, checksum generator551. More specifically, encrypted PDM data 73, for Frame N (generated byinputting an output of pseudo random bit stream generator 552 andsigma-delta generator 12 into XOR logical gate 58), is loadedsimultaneously with the FCS delay gap 710, the FCS checksum 712, and theinterframe gap 714, all corresponding to Frame N-1 and then continuingwith the Ethernet frame prefix 702, IP/UDP prefix 704, payload preamble706, all corresponding to Frame N.

The Ethernet PDM transmission 75 is unloaded from first FIFO memory 54during each Ethernet frame such that the FCS delay gap, which mayconsist of padding zero ‘0’ bits, commences unloading immediately at thebeginning of each Ethernet unloading frame.

Refer now to FIG. 9 which shows a networked digital audio distributionsystem 100 in accordance with one illustrative embodiment of the presentinvention. There are a plurality, such as seven, IP PDM audiotransmitters 5A-5G, each of which produce an Ethernet PDM transmission75 including 1-channel of encrypted PDM data, as described above forFIGS. 5 and 7 . Accordingly, each of the IP PDM audio transmitters 5A-5Goutput a sequence of Ethernet PDM transmissions 75, as described abovein FIG. 7 , among other Figures, and each of the Ethernet PDMtransmissions 75 includes an encrypted PDM data payload 709 portion thatconsists of a single channel of audio data corresponding to theparticular output of a single one of the IP PDM audio transmitters 5A-5G(i.e., one Ethernet PDM transmission 75 for each of the IP PDM audiotransmitters 5A-5G).

Ethernet router and processor 3 accepts a plurality, such as seven, ofsets of sequential Ethernet frames, each corresponding to one of theplurality of IP PDM audio transmitters 5A-5G. The Ethernet router andprocessor 3 extracts the individual Ethernet PDM frame data 74,consisting of 4 bytes of data, from each one of the plurality of IP PDMaudio transmitters 5A-5G, and forms a combined encrypted data portion,encrypted PDM data payload 709, consisting of 28 bytes of datacorresponding to seven audio channels with 4 bytes per channel. Afterproducing this combined encrypted data portion (encrypted PDM datapayload 709), Ethernet router and processor 3 outputs the combinedencrypted data portion as combined Ethernet PDM transmission 76including multi-channel encrypted PDM data sequences to each of aplurality of IP PDM audio receivers, including for example IP PDM audioreceiver 9, which can accept a multi-channel input.

Refer now to FIG. 10 and continue to refer to FIG. 9 . The combinedEthernet PDM transmission 76, containing multi-channel encrypted PDMdata, is received at Ethernet interface 26, which then transfers thedata contained within the transmission, in the form of Ethernet PDMtransmission 75, to FIFO memory 94. The Ethernet PDM transmission 75 isreconstructed into a plurality of encrypted PDM 1-bit data streams83A-83G by unloading FIFO memory 94 in a manner similar to the thatdescribed for the unloading of second FIFO memory 64 in the descriptionfor FIG. 6 given above.

A plurality of unencrypted PDM 1-bit data streams 82A-82G are recoveredfrom the corresponding plurality of encrypted PDM 1-bit data streams83A-83G using a plurality of XOR logic gates 98A-98G and a plurality ofpseudo-random 1-bit data streams 89A-89G in a manner similar to thatdescribed for the XORing function of second XOR logic gate 68 in thedescription for FIG. 6 given above. In one illustrative embodiment ofthe present invention, the plurality of pseudo-random 1-bit data streams89A-89G are produced by a corresponding plurality of pseudo random bitstream generators 95A-95G, each being a functional component withinprocessor and memory 90.

Each of the plurality of unencrypted PDM 1-bit data streams 82A-82G isdecimated into a corresponding plurality of PCM N-bit data streams81A-81G using a plurality of decimator filters 93A-93G in a mannersimilar to that described for decimator filter 13 in the description forFIG. 6 given above.

Each of the plurality of PCM N-bit data streams 81A-81G is accepted asan input to digital audio mixer 99 where they are combined usingalgorithms known in the art including, for example, such functions asadjusting individual volume levels, bass/treble, and phase shift.Digital audio mixer 99 outputs a combined PCM N-bit digital data stream77 that has been created from the outputs from each of the plurality ofIP PDM audio transmitters 5A-5G, shown in FIG. 9 .

The combined PCM N-bit digital data stream 77 is converted into acombined analog output signal 37 using DAC 27 in a manner similar tothat described for DAC 27 in the description for FIG. 6 given above.Finally, the combined analog output signal 37 is sent to loudspeaker 21.

The disclosed embodiments provide systems, methods, and modes forsecurely distributing, with minimal latency, one or more 1-bit encrypteddigital audio signals over a network using IP or other user definedprotocols. It should be understood that this description is not intendedto limit the embodiments. On the contrary, the embodiments are intendedto cover alternatives, modifications, and equivalents, which areincluded in the spirit and scope of the embodiments as defined by theappended claims. Further, in the detailed description of theembodiments, numerous specific details are set forth to provide acomprehensive understanding of the claimed embodiments. However, oneskilled in the art would understand that various embodiments may bepracticed without such specific details.

Although the features and elements of aspects of the embodiments aredescribed being in particular combinations, each feature or element canbe used alone, without the other features and elements of theembodiments, or in various combinations with or without other featuresand elements disclosed herein.

This written description uses examples of the subject matter disclosedto enable any person skilled in the art to practice the same, includingmaking and using any devices or systems and performing any incorporatedmethods. The patentable scope of the subject matter is defined by theclaims, and may include other examples that occur to those skilled inthe art. Such other examples are intended to be within the scope of theclaims.

The above-described embodiments are intended to be illustrative in allrespects, rather than restrictive, of the embodiments. Thus, theembodiments are capable of many variations in detailed implementationthat can be derived from the description contained herein by a personskilled in the art. No element, act, or instruction used in thedescription of the present application should be construed as criticalor essential to the embodiments unless explicitly described as such.Also, as used herein, the article “a” is intended to include one or moreitems.

All United States patents and applications, foreign patents, andpublications discussed above are hereby incorporated herein by referencein their entireties.

INDUSTRIAL APPLICABILITY

To solve the aforementioned problems, the aspects of the embodiments aredirected towards systems, methods, and modes for securely distributing,with minimal latency, one or more 1-bit encrypted digital audio signalsover a network using Internet Protocols.

List of Acronyms Used in the Specification in Alphabetical Order

The following is a list of the acronyms used in the specification inalphabetical order.

-   -   Σ-Δ sigma-delta (analog to PDM modulator)    -   ADC analog-to-digital converter    -   AV audio-video    -   CD compact disc    -   DAC digital-to-analog converter    -   DFT Discrete Fourier Transform    -   FIFO first-in, first-out memory    -   FCS frame check sum    -   IEEE Institute of Electrical and Electronics Engineers    -   IC Integrated Circuit    -   IP Internet protocol    -   kHz kilohertz    -   LAN local area network    -   Mbps megabits per second    -   MEMS micro-electro-mechanical system    -   MHz megahertz    -   N an integer having a predefined value    -   N−1 an integer having a predefined value that is one less than N    -   N+1 an integer having a predefined value that is one greater        than N    -   N-bit a predefined number of bits (such as 8, 12, 16, or 24)    -   OSR oversampling rate    -   PCM pulse code modulated    -   PDM pulse density modulation    -   PHY Ethernet physical layer (transmission path)    -   UDP user defined protocol    -   XOR exclusive-or (logic gate)

Glossary of Terms Used in the Specification in Alphabetical Order

The following is a non-limiting, glossary of terms used in thisdescription of the aspects of the embodiments.

-   100BaseT Ethernet standard for 100 Mbps data transmission over    unshielded twisted pair wiring.-   dither a noise-like signal added before quantization to improve    performance.-   IEEE 802.3 A working group and a collection of IEEE standards    produced by that working group defining the physical layer and data    link layer's media access control of wired Ethernet.-   linearization the process of mitigating the deleterious effects of    data quantization, usually by adding dither.-   noise modulation the undesirable variation of the noise floor in a    system due to the signal content-   sampling rate the rate at which a signal is sampled to produce a    discrete-time representation-   word length the number of bits used to represent a digital sample-   quantization a procedure for representing an arbitrary data sample    using a given word length.

Alternate Embodiments

Alternate embodiments may be devised without departing from the spiritor the scope of the different aspects of the embodiments. For example,an unencrypted 1-bit PDM stream from a microphone unit could betransmitted within Ethernet data packets to an encrypting unit whichproduces an encrypted 1-bit PDM stream as described above.Alternatively, additional audio processing could be performed within theinventive IP PDM audio receivers, such as for example echo cancellation.

What is claimed is:
 1. A method for transmitting encrypted audio dataover an Ethernet connection, said method comprising the steps of: (a)converting an audio input signal into a first pulse density modulated(PDM) 1-bit data stream at a first predetermined audio oversamplingrate; (b) producing an encrypted PDM 1-bit data stream byexclusive-or-ing (XORing) the pulse density modulated 1-bit data streamwith a first pseudo-random 1-bit data stream; (c) packaging theencrypted PDM 1-bit data stream into Ethernet PDM frame data by loadinga first first-in first-out (FIFO) memory at the first predeterminedaudio oversampling rate and unloading said first FIFO memory at a firstpredetermined Ethernet physical layer (PHY) transfer rate; (d)transmitting and receiving said Ethernet PDM frame data from a firstEthernet interface to a second Ethernet Interface; (e) reconstructingthe encrypted PDM 1-bit data stream from the Ethernet PDM frame data byloading a second FIFO memory at a second predetermined Ethernet PHYtransfer rate and unloading said second FIFO memory at a secondpredetermined audio oversampling rate; (f) recovering the first PDM1-bit data stream by XORing the encrypted pulse density modulated 1-bitdata stream with a second pseudo-random 1-bit data stream; (g)decimating the first PDM 1-bit data stream into a pulse coded modulated(PCM) N-bit digital data stream at a predetermined audio sampling rate;and (h) converting the N-bit PCM digital data stream into an analogoutput signal; wherein said first and second pseudo-random 1-bit datastreams comprise identical bit sequences at a predetermined encodingrate; and the steps of producing and reconstructing the encrypted PDM1-bit data stream by XORing are performed at said predetermined encodingrate.
 2. The method of claim 1, wherein: the N-bit PCM digital datastream is a 16-bit pulse code modulated digital data stream.
 3. Themethod of claim 1, wherein: said first and second predetermined audiooversampling rates are both a same integer multiple of the predeterminedaudio sampling rate.
 4. The method of claim 1, wherein: saidpredetermined encoding rate is an integer multiple of the predeterminedaudio sampling rate.
 5. The method of claim 1, wherein: saidpredetermined audio sampling rate is an integer multiple of thepredetermined encoding rate.
 6. The method of claim 1, furthercomprising the steps of: (i) transmitting and receiving a unique seedvalue from the first Ethernet interface to the second EthernetInterface; (j) computing said first pseudo-random 1-bit data streambased on this unique seed value; and (k) computing said secondpseudo-random 1-bit data stream based on this unique seed value.
 7. Aninternet protocol (IP) pulse density modulation (PDM) audio transmitterapparatus adapted to transmit an encrypted PDM 1-bit data stream over anEthernet network, said apparatus comprising: (a) an acoustic sensorelement; (b) a sigma-delta modulator adapted to convert an analog inputsignal into a pulse density modulated 1-bit data stream at apredetermined audio oversampling rate; (c) a processor and memoryadapted to compute and produce a first pseudo-random 1-bit data streamat a predetermined encoding rate; (d) a first exclusive-or (XOR) logicgate operatively connected to the pulse density modulated 1-bit datastream and the pseudo-random 1-bit data stream in such a manner as toproduce an encrypted pulse density modulated 1-bit data stream at thepredetermined audio oversampling rate; (e) a first first-in first-out(FIFO) memory configured to load the encrypted pulse density modulated1-bit data stream at said predetermined audio oversampling rate and tounload Ethernet pulse density modulated frame data at a predeterminedEthernet physical layer (PHY) transfer rate; and (f) an Ethernetinterface configured to accept the Ethernet frame data at thepredetermined Ethernet PHY transfer rate and to transmit Ethernet datapackets on a network.
 8. The apparatus of claim 7, wherein: saidacoustic sensor element is a micro-electrical-mechanical system acousticsensor element.
 9. The apparatus of claim 7, wherein: said predeterminedaudio oversampling rate is an integer multiple of the predeterminedencoding rate.
 10. The apparatus of claim 7, wherein the processor andmemory are further adapted to: (a) compute a frame checksum (FCS); (b)compute a payload preamble; and (c) load each of said frame checksum andpayload preamble into the FIFO memory.
 11. The apparatus of claim 10,wherein the payload preamble includes a time stamp.
 12. The apparatus ofclaim 7, wherein the processor and memory are further adapted to: (a)store a predetermined frame checksum (FCS) delay gap; (b) store apredetermined interframe gap; (c) store a predetermined Ethernet frameprefix; (d) store a predetermined internet protocol/user definedprotocol (IP/UDP) prefix; and (e) load each of said FCS delay gap,interframe gap, Ethernet frame prefix, and IP/UDP prefix into the FIFOmemory.
 13. An internet protocol (IP) speaker apparatus adapted toreceive a 1-channel encrypted pulse density modulation (PDM) 1-bit datastream over an Ethernet network, said apparatus comprising: (a) anEthernet interface configured to receive Ethernet data packets on anetwork; (b) a first-in first-out (FIFO) memory configured to load theEthernet data packets at a predetermined Ethernet physical layer (PHY)transfer rate and to unload an encrypted pulse density modulated 1-bitdata stream at a predetermined audio oversampling rate; (c) a processorand memory adapted to compute and produce a pseudo-random 1-bit datastream at a predetermined encoding rate; (d) an exclusive-or (XOR) logicgate operatively connected to the encrypted pulse density modulated1-bit data stream and the pseudo-random 1-bit data stream in such amanner as to produce an unencrypted pulse density modulated 1-bit datastream at said predetermined audio oversampling rate; (e) a decimatorfilter adapted to convert the unencrypted pulse density modulated 1-bitdata stream into a pulse code modulated N-bit digital data stream at apredetermined audio sampling rate; (f) a digital to analog converteradapted to convert the N-bit pulse code modulated digital data streaminto an analog output signal at said predetermined audio sampling rate;and (g) a loudspeaker configured to receive the analog output signal.14. The apparatus of claim 13, wherein: the N-bit pulse code modulateddigital data stream is a 16-bit pulse code modulated digital datastream.
 15. The apparatus of claim 13, wherein: (a) said predeterminedaudio oversampling rate is an integer multiple of the predeterminedencoding rate.
 16. An internet protocol (IP) loudspeaker apparatusadapted to receive a multi-channel encrypted pulse density modulation(PDM) 1-bit data stream over an Ethernet network, said apparatuscomprising: (a) a first-in first-out (FIFO) memory configured to loadEthernet data packets at a predetermined Ethernet physical layer (PHY)transfer rate and to unload a plurality of encrypted pulse densitymodulated 1-bit data streams at a predetermined audio oversampling rate;(c) a processor and memory adapted to compute and produce a plurality ofpseudo-random 1-bit data streams at a predetermined encoding rate; (d) aplurality of exclusive-or (XOR) logic gates, each of said XOR gatesoperatively connected to a corresponding one of said plurality ofencrypted pulse density modulated 1-bit data streams and a correspondingone of said plurality of pseudo-random 1-bit data streams in such amanner as to produce a corresponding plurality of unencrypted pulsedensity modulated 1-bit data streams at said predetermined audiooversampling rate; (e) a plurality of decimator filters adapted toconvert each of said plurality of unencrypted pulse density modulated1-bit data streams into a corresponding plurality of N-bit pulse codemodulated (PCM) digital data streams at a predetermined audio samplingrate; (f) a digital audio mixer configured to accept the plurality ofN-bit pulse code modulated digital data streams and to produce acombined pulse code modulated N-bit digital data stream multi-channeloutput; (g) a digital to analog converter adapted to convert thecombined PCM N-bit digital data stream into an analog output signal atsaid predetermined audio sampling rate; and (h) a loudspeaker configuredto receive the analog output signal.
 17. The apparatus of claim 16,wherein: (a) the combined PCM N-bit data stream is a PCM 16-bit digitaldata stream.